The How Matters: Simulation-Based Assessment of the Potential Contributions of Lateral Flow Device Tests for Keeping Schools Open and COVID-Safe in England

Environments where exact contact tracing is infeasible pose a challenge to ‘test and trace’ approaches for containing infectious diseases like COVID-19 that rely on following up on the close contacts of an index case. This is particularly problematic in primary schools and some workplaces. The additional benefit of using rapid screening tests over mere isolation restrictions of contacts has repeatedly been put forward for schools in the United Kingdom as potentially leading to improved containment and less absence from school for the pupils, but setting up randomized comparisons in primary schools is particularly challenging. Investigating this issue continues to be relevant as many countries take similar steps and more infectious mutations of the virus emerge while pupils, especially young ones, remain largely unvaccinated. We use a customized agent-based simulation to assess the impact of different test and isolation schemes on containment of outbreaks and school days missed in a primary school setting. The simulation links the screening test sensitivity and the infection risk to each individual’s latent viral load. Robustness with respect to a number of criticisms of previous models is assessed by extensive sensitivity analyses. We made the core functionality of our simulation tool available as an interactive web app allowing investigators to explore parameter ranges relevant to their scenario of interest. Reactive use of repeated lateral flow device (LFD) screening tests (‘test for release’) is less effective than regular whole school cross-sectional testing in primary schools and comparable settings and the influence of screening test sensitivity is secondary to that of other key parameters that impact transmission. Results are stable with respect to a wide range of previously debated additional factors like test-retest autocorrelation, imperfect test compliance, and assumptions on the dynamics of viral loads in infected individuals. Our findings support the adoption of regular (e.g, once- or twice-weekly) cross-sectional testing to contain COVID-19 in primary school settings.